[BB_TX]

First time I have heard of a propane tank stolen, although I often look inside the doors of mine just to make sure they are still there.
The padlock on the strap is the best idea. The little tubular locks on the doors do little more than keep nosy people out and honest people honest. I had my basement broken into while in storage, both sides, and stuff stolen. They apparently used a screwdriver or similar object, but left just very small marks where they pried them open. The locks were still in the locked position, tabs slightly bent.